Saturday, October 30, 2010


We came upon this male field grasshopper Chorthippus brunneus sunbathing on the steps down to Hawthorn Hive on the Durham Coast, this afternoon. His courting days are over and he was making the most of the warm mid-day sun, before the frosts arrive and bring an end to his short life. Somewhere there will be packets of eggs, carefully inserted amongst grass roots by his mate who he would have serenaded by sawing the pegs on his legs back and forward across those membranous wings, in the process of stridulation.  Next spring they'll hatch and the nymphs that emerge will grow and moult four times before they reach maturity - and then the next generation of chirruping grasshoppers will begin the whole cycle all over again.
You can listen to a field grasshopper's song here

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Friday, October 29, 2010

A Tree-Spotter's Guide to Bark: Part 1

When you think about it, the bark of a tree is pretty remarkable. It's the tree's self-healing protective layer, defending the thin layer of living phloem cells inside, just below the surface, that conduct sugars up and down the stem and also protecting the living layer of cambial cells that produces new growth every year. It's waterproof, but it lets gases pass in and out and it's capable of expanding to keep pace with the growth of the tree, splitting and cracking as the tree ages in a pattern that's characteristic of each tree species. On one January day twenty-seven years ago the bark of this beech Fagus sylvatica was the canvas on which SP and CS carved a declaration of their undying affection; thankfully the wound healing properties of the bark meant that the tree still thrives, even though the union of SP and CS may or may not have endured.

The bark is a tree species' fingerprint. This is Scots pine Pinus sylvestris, with its irregular plates of warm red-brown bark that perfectly complement the deep, glossy green of its needles - especially when winter sunlight strikes the trunk.

The barks of pedunculate oak Quercus robur and of Durmast oak Q. petraea can't really be distinguished, so this could be either (although I happen to know that it was the latter because the acorns had no stalks). I think it may generally be the case that slow-growing trees like oak develop a rugged bark of ridges and fissures that are slowly added to with age, while fast growing species like sycamore and birch tend to develop more rugged splits or shed bark more readily. 

Sycamore Acer pseudoplatanus bark is smooth when the tree is young but soon develops into flattened, irregular plates that are slowly shed as the tree ages, flaking away to reveal a fresh layer below.

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Thursday, October 28, 2010

A Tree-Spotter's Guide to Fruits and Seeds: Part 5

This little huddle of 7-spot ladybirds, apparently settling down for communal hibernation, were a bit premature in their choice of these unripe alder Alnus glutinosa cones as a resting place last week. Within a few days the cones will begin to ripen ....

... become woody and spit open. You can just see the tiny chestnut-brown seeds inside. They are an important food source for many birds in winter and are released in vast numbers from now until January. The tree will be flowering again in February and you can see next year's embryonic cones already formed - they are the little knobbly things on stalks, top left, next to the bud at the tip of the shoot. Above the ripening cones you can also see next spring's male catkins already forming.

Alder cones tend to stay attached to the tree for a long time - these old ones would have shed their seeds back in October-November 2009.

Ever since grey squirrels moved into my part of Durham it has become harder to find fully ripe hazel Corylus avellana nuts - the squirrels take them while they are still at this green stage. Filberts are cultivated hazels that have much longer leafy bracts sheathing the nuts.
Wild cherry or gean Prunus avium fruit ripens in July. A couple of years ago I did a taste test on as many different fruit-bearing wild cherry trees as I could find. They were surprisingly variable - most were breathtakingly sour but a few were sweet enough to eat. The hard seed inside the fruit is a favourite food of hawfinches - one of the few birds with a beak that's powerful enough to crack it open. Everytime I see a tree in fruit I scan the ground below for a hawfinch eating the seeds from rotting fruits: no luck so far but I live in hope...... The hard cherry stones are also popular with field mice. When I demolished our old garden shed I found a mouse's stash of scores of cherry stones from the tree that used to grow in our garden hedge, each with a neat hollow nibbled in it.
Professional foresters can identify conifers just by crushing their needles and sniffing their resinous aroma. This is one of the easier ones for scratch-and-sniff botany - Western Hemlock Tsuga heterophylla (which is not related to the hemlock that poisoned Socorates). Apart from the hint of citrus scent in its resin (some say it smells like ground elder), it bears these small purplis cones and the shoots carry needles of varying lengths. It's a native of the west coast of North America, but often seen in forestry plantations in Britain, especially on the wetter western side.

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Middlehope Burn, Weardale

Today's Guardian Country Diary traces the route through the old lead mine ruins along Middlehope Burn at Westgate in Weardale. It's hard to believe now but this wooded, steep-sided valley was once a cradle of industry, whose heyday was during the 19th. century. The geology here is composed of alternating beds of limestone, sandstone and shale that erode at different rates and create perfect conditions for the formation of waterfalls like this one next to the cornmill, where the burn cascades over sandstone and greets the visitor on arrival. Rich mineral veins run up through fissures in the strata from the volcanic whin sill below.

The path up the valley is often washed away and has recently been repaired after floods in 2008 and 2009. When there's torrential rain on the fells above, a torrent of water flows down the burn, towards the River Wear. The burn is perfect dipper habitat and the mine ruins upstream provide ideal nest sites.

The first ruins you reach are the Low Slitt Mine bousteads, where partnerships of miners stored their ore before it was crushed between metals rollers. Each compartment belonged to a different partnership. At this point there are mine levels - horizontal tunnels that stretched sometimes for several miles into the hillsides, just large enough to accommodate a pony and its load. There was also a shaft here, at 177 metres deep the deepest in Weardale, where miners were lowered using an Armstrong hydraulic engine. The engine is long gone but its massive mountings lie just around the corner, out of sight in this photograph. Across the burn from the engine lies the old waterwheel pit that also powered machinery. The energy of flowing and stored water provided the power for the whole enterprise.

Further up the valley, where it broadens out into the fells, lies the ruins of Middlehope Shield Mine. Photographs from the beginning of the 20th. century, shortly before the mines closed for good, show gantries of ore crushing machinery here but now all that remains are the jagged ruins of the masonry.

The lead mined here was used for everything from sealing church roofs to producing bullets for some of greatest battles in 19th. century history. Lead, in the form of galena, was separated from the lighter crushed rock on washing floors, using a current of water channeled from reservoirs and from the burn. Now this waterlogged fenny turf is home to plants like the insect-eating butterwort and is a breeding site for frogs and dragonflies. At the head of the valley, at the bottom of the fell in the centre distance, lies yet another mine level that was briefly reopened to mine fluorspar. The whole valley was a cauldron of activity during the industrial revolution but now it's a designated Site of Special Scientific Interest and part of the North Pennines Area of Outstanding Natural Beauty - and a European Geopark. Nature has worked wonders at healing the scars over the last century.

On a mellow autumn afternoon it's hard to imagine the cacophony of noise and the dirt and dust that must have filled the valley. The drier areas are now pasture, providing fine conditions ......

... for a range of grassland fungi, like this little gem with gills like cathedral vaulting... which I think may be a snowy waxcap Hygrocybe virginea (?), which sometimes develops with a funnel-shaped cap.
These, I've yet to identify (anybody know what they are?)... I think they could be dung roundheads Stropharia semiglobata

... and this is meadow coral Clavulinopsis corniculata still in the early stages of growth.

All the power for the mine machinery came from the skillful management of flowing water, channeled from the burn and tributaries, but no one seems absolutely sure where all the channels were. Floods have deposited rock and silt as the burn has changed its course, but here and there underground channels like this one bubble to the surface then disappear into the depths again.

Looking back as you climb up out of the valley you can see traces of the railway that carried the ore away from the site. The ruins of Middlehope Shield Mine lie amongst the trees in the centre middle distance and to the left of those are washing floors and yet another mine level (White's Level) cut into the hillside. The bridge abutments in the foreground carried the mineral railway over the burn.

Climb higher still and you can see the track bed of another railway - the smooth green track running slightly downhill to the right from the centre of this picture, just above a wall. In the distance, rays of sunshine are sweeping across the flanks of Chapel Fell that looms up out of the haze.
At the top of the fell now, and the sun is lighting up West Slitt Dam, the reservoir whose water provided the power for the Armstrong hydraulic engine below, that hauled miners up from their underground tunnels.

There were levels cut to mine lead all the way up the fellside. The green tracks fanning out here are soil tips, where ponies dragged carts of rock waste and dumped it.
At the end of a long shift underground hewing rock, this is the panorama that they would have enjoyed when they trudged wearily back down the hill into Westgate. It was a hard way to earn a living.

If you are interest in this circular walk, you can download an excellent Geotrail here.

Adrian's Images has a photo of the starting point for the walk - the footpath up to the strangely-named Weeds, at the lay-by in the centre of Westgate, here.

Monday, October 25, 2010

A Tree-Spotter's Guide to Fruits and Seeds: Part 4

A really good crop of beech Fagus sylvatica nuts is good news all round for wildlife, providing a food resource that lasts well into the winter. Bramblings are particularly fond of these seeds and in past 'mast years' I've sometimes seen large flocks of these finches in the beech woods at Stanhope Dene in Weardale, feasting on the fallen nuts.

We have three tree species in the genus Acer that commonly occur in the countryside but only this one - field maple Acer campestre - is native. It grows into a small hedgerow tree. The yellow autumn foliage is attractive and the winged fruits are unmistakeable. In field maple the wings of the fruits (which, botanically, are known as samaras) are held out almost horizontally, unlike .....
... those of the non-native sycamore Acer pseudoplatanus, whose wings are swept back at an angle of about 45 degrees. Sycamore is native to the mountains of central and southern Europe but has spread throughtout Britain since it was introduced in the fifteenth century.

The wings on Norway maple Acer platanoides fruits are held at an angle intermediate between field maple and sycamore, at about 30 degrees to the horizontal, and they are larger, broader-winged and altogether more attractive than either of the other species. They are also very efficient fliers - my garden is infested with seedlings that have arrived as an airborne invasion from a tree upwind of us.

Sycamore's autumn foliage of often marred by the black spots of tar-spot fungus and simply turns brown and withers in autumn, unlike the leaves of the closely-related Norway maple whose foliage turns a clear, vibrant yellow. This Norway maple tree, photographed at the weekend growing in a crevice in a  quarry wall at Stanhope in Weardale, is testament to the mobility of the winged fruits and the dazzling autumn display that the tree delivers.

Sea buckthorn Hippophae rhamnoides is more of a shrub than a tree, although I know of some specimens of a similar height and stature to large elders. At this time of year it produces a heavy crop of these dazzling orange berries that birds seem to ignore. Sometimes the fruits just decay on the branches and on warm spring days develop a rancid, vinegar-like smell. The underside of the leaves is coated in flat grey scales, that protect the plant against excessive water loss in the windy coastal habitats where it thrives, while its vicious thorns turn it into impenetrable scrub - good nesting territory for birds.

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Saturday, October 23, 2010

A Tree-Spotter's Guide to Fruits and Seeds: Part 3

European larch Larix europaea is our only deciduous conifer so it should be easy to identify, but there are two Larch species grown in Britain and a hybrid between them, so it's sometimes tricky to identify a tree unequivocally. Unlike their needles, larch cones stay attached to the twigs for several years and this one, with wavy-edged cone scales that hardly curve outwards at the tip, is L. europaea. European larch has elegant pendulous branches that can sweep down to ground level and if it's given space to grow it will become a graceful specimen tree; sadly, most are destined to grown at close spacings in plantations.

Faster-growing Japanese larch Larix kaempferi produces cones with scales that are emphatically curled outwards and downwards at the rim. The extremely vigorous hybrid between L. europaea and L. kaempferi, known as Dunkeld larch L. x eurolepis has cones that are similar but the lip curls outwards without curving downwards .... but, when this hybrid then crosses with L. kaempferi it all gets very confusing....
When I was a kid, my parents took me Christmas shopping in Charlotte Street market in Portsmouth, where there were hot chestnut sellers on street corners who would serve you up a brown paper bag full of smouldering chestnuts that you had to toss from hand to hand until they were cool enough to peel. They probably imported their chestnuts from southern France, or Spain where the tree is native. Sweet chestnut Castanea sativa was brought to England by the Romans, who recognised the value of its nuts and coppiced timber. It needs a good summer to produce chestnuts that are worth roasting here in County Durham - and this hasn't been one of them. Most British trees produce several small nuts per spiny fruit, rather than one large one.

Autumn, when acorns are ripening,  is the best time to identify our two native oak species. The sessile or Durmast oak Quercus petraea bears acorns that have little or no stalk.

English or pedunculate oak Quercus robur acorns dangle from a long stalk (peduncle). Occasionally the two species form hybrids, bearing acorns on short stalks. Oaks, like beech trees, tend to bear heavy crops of seeds on alternate years ('mast' years). It's a mast year for oaks in Durham city this year and they are lying thick on the ground, attracting flocks of pigeons and a lot of jays that are carrying them away to bury for winter emergency rations - if they ever remember where they have buried them. Last year there was hardly an acorn to be found under the same trees.


Elder Sambucus nigra berries are popular for making home-made wine but they also have a history of use as a source of dye. Freshly dyed fabric tends towards a rich brown but addition of metal salts like aluminium, chrome and copper as mordants produces subtler shades that vary from umber to blue, violet, grey and through to black, although they all tend to fade after a while in bright light.

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Thursday, October 21, 2010

A Tree-Spotter's Guide to Fruits and Seeds: Part 2

Yew Taxus baccata, one of only three native conifers in Britain (the others are Scots pine and juniper) is a conifer that doesn't produce cones. The vast majority of its relatives carry seeds on the surface of whorls of woody bracts that form a cone, but yew produces single seeds surrounded by a red fleshy aril. In the picture above you can see an aril that has yet to swell and envelope its seed, just above and to the right of the seed in the centre of the image. Thrushes are particularly fond of the succulent aril. All parts of the tree are very poisonous apart from this conspicuous coat but the thick hard wall of the poisonous seed (which can take two years to germinate) means that it can pass through the bird's gut with no ill effects. There are separate male and female yew trees, so any that are not bearing seeds at this time of year are probably male. There is a rare mutant of yew (which I have never seen) known as var. lutea that bears yellow arils. In Sussex you can find one of the finest of all yew forests, at Kingley Vale National Nature Reserve, filled with venerable trees whose dense shade prevents anything from growing beneath them -well worth a visit if you are ever in that part of the country. Some churchyard yews in various parts of Britain are reputed to be over 2000 years old.

Usually privet Ligustrum vulgare grows as a shrub and is often clipped into a neat hedge, but it it's allowed to grow unchecked it will grow into a small tree, flowering prolifically, attracting butterfly and bee pollinators and producing these rather attractive indigo-hued berries. It's a member of the olive family (Oleacea), as is ...

... the common ash Fraxinus excelsior. Ash trees can be either male, female or hermaphrodite and it's only the latter two forms that bear these familiar ash 'keys', in large bunches. Ash seeds are dormant and can take up to 18 months to germinate. They begin to fall in late autumn and require a winter chill before any will germinate - and even then only a small percentage of the crop sprouts in spring. The rest are immature and the embryos inside continue to develop throught the summer, on the tree or on the ground, and will not germinate until the following spring.

Some potential ash seeds never mature, if the flowers are attacked by a microscopically-small gall-mite called Eriophyes fraxinivorus (also known as Aceria fraxinivorus). Trees like this one alongside the River Tyne at Wylam can become completely infested and produce few seeds.

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Sunday, October 17, 2010

Birch Bolete

We found this fine specimen of a birch bolete Leccinum scabrum (and numerous others like it) amongst the silver birches on the edge of the golf course at Wylam beside the River Tyne yesterday. This bolete is always found near birch trees because its underground hyphae form a mutually beneficial relationship - a mycorrhizal association - with the roots of the tree. The fungus helps the tree absorb essential minerals like phosphorus from the soil in exchange for some of the sugars that the tree manufactures.
What I find most remarkable about toadstools is the way in which that mass of diaphenous, microscopically fine underground hyphae come together to form these wonderful three-dimensional structures. How do all those simple threads communicate and collaborate to form the stipe, the cap and - most remarkably of all - all those pores through which the spores are shed? Where does the control centre for this self-assembly process lie? Botany text books can describe with great precison how plants control their development via highly organised growing points (meristems) to produce roots, shoots, bramches, flowers and leaves but the way in which toadstools are built is much less well understood.

The gills under a toadstool's cap (or in this case the pores) must always remain perfectly parallel to the force of gravity if the spores that line them are to drop down and escape into the airstream. Displace a toadstool from the vertical and the gills will realign with gravity very quickly. The process is slower in polypores like this (and they have stouter stipes to keep them vertical) but they still adjust their growth to realign vertically.

It seems to me that a complex toadstool is one of evolution's most amazing, least celebrated, and poorly understood achievements...

Friday, October 15, 2010

A Tree-Spotter's Guide to Fruits and Seeds: Part 1

Surely the most gaudy tree in the British flora - spindle Euonymus europaeus. Spindle has been eradicated from hedgerows in some parts of the country because it acts as a winter host for the black bean aphids that infect field bean crops. That's a pity, because I can think of no other hedgerow  tree that presents such a colourful sight in autumn, when the leaves turn crimson and it produces these dangling shocking pink fruits that split open to reveal vivid orange seed. That soft orange outer layer is an aril - an extra seed coat layer that has evolved to attract birds that eat them and void the undigested hard seed seed through their gut. Arils are quite common in tropical fruits (the edible part of a lychee is an aril) but are uncommon in temperate floras.

Catkins of silver birch Betula pendula seeds ripen in late summer and begin to break up now - as these are doing - sending down showers of tiny winged seeds. Silver birch seed is a key food source for many finches in winter, including siskins and redpolls. The seeds can be produced in vast quantities - I was recently sent some samples to identify by a train company whose trains were breaking down because of overheating caused by engine air intakes becoming blocked by seeds from lineside birch trees. 

Indisputably a hawthorn - but which species? Common hawthorn Crataegus monogyna or Midland hawthorn C. laevigata? Now's the time to find out, by splitting open the fruit (which in botanical terns is a drupe, not a true berry). If there's one seed inside it's common hawthorn, if there are two then it's the midland hawthorn. This one had one-seeded fruits, so it's common hawthorn.

The powdery bloom on the outside of a sloe Prunus spinosa is a natural wild yeast that feeds on sugars that are produced in the fruit - although you'd be hard-pressed to detect any sweetness in the flesh of these incredibly bitter drupes. These two, and a couple of hundred others like them, are now bottled in gin in the cupboard under our stairs - and the resulting sloe gin should be ready for Christmas.

Hornbeam Carpinus betulus, famous for the hardness of its timber that was once used to make rake teeth and other similarly durable wooden items, bears these little pagodas of fruits that turn bright yellow with the foliage in autumn but remain on the tree for a while after the leaves drop, creating an effect a little like Christmas tree decorations. 

The hard seeds are nutlets, each attached to its own three-lobed bract that spins to the ground when it's released from the cluster.

For a Tree-Spotter's Guide to Buds, visit

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